Discharge apparatus containing gas or vapor



Dec. 22, 1936. w. DALLENB/ACH DISCHARGE APPARATUS CONTAINING GAS OR VAPOR Filed Oct. 22,- 1935 2 Sheets-Sheet l LO 5 A? Mmniar (11a ZIGPDZIZZGXIba 0/1 a 220))? e75 I Dec. 22, 1936. "w. DALLENBACH 2,065,259

DISCHARGE APPARATUS CONTAINING GAS OR VAPOR Filed Oct. 22, 1935 2 Sheets-Sheet 2 v ln z/enior" MaZZerDdNenbach Patented Dec. 22, 1936 UNITED STATES ATENT OFFICE Walter Dallcnbach, Berlin-Charlottenbnrg, Germany Application October 22, 1935, Serial No. 46,219 In Germany October 23, 1934 15 Claims.

My invention relates to discharge apparatus containing gas or vapor. The vacuum vessel is separated from the vacuum pump and encompasses a plurality of anodes encased by anode sleeves or other parts which, at certain phases of operation of the apparatus, bring about an impoverishment of ions in the vicinity of the anodes. My invention is particularly intended for mercury vapor rectifiers, preferably for such rec tifiers having great capacity.

In my pending application S. N. 745,353, filed on September 24, 1934, I have described such vacuum vessels as mentioned above and as charged with a rare gas, the pressure of which amounts drargyrum). With a cold cylinder where the stream of gas or vapor, rising from the cathode (for example, a stream of mercury vapor), is of too low a value, and also with high current intensities, an impoverishment of ions in the vicinity of the anodes will occur. Such impoverishment may result in excess voltages, high-frequency oscillations and striking back, but can be prevented by filling-the vessel with a rare gas of the magnitude mentioned. The use of rare gas has, however, apart from these advantages, certain disadvantages.

The occurring drop of arc is higher when using rare gases than merely with mercury vapor. The behavior of the separate rare gases rather differs in this respect. It has been ascertained by extensive experiments that helium and neon only can then be used, if comparatively high drops of arc can be admitted and this amounts with helium, for example, to from 50-60 volts, and with neon to from 30-40 volts. Argon and krypton have proved to be very much more favorable, krypton being most favorable, but also with these gases the drops of are are still somewhat higher than with pure mercury vapor where the drops of arc amount to about to volts.

Furthermore, pure mercury vapor exhibits, in contradistinction to the blocking voltages, a lesser tendency for the occurrence of glow discharges and back striking. That is, with a given blocking voltage in mercury vapor a glow discharge ignites only at higher voltages than in krypton or. argon, and after the glow discharge once has ignited, it attains in mercury vapor lower current in- 60 tensities than in argon or krypton.

Furthermore, argon, as well as krypton will be consumed, although to a slight extent only, if they are permanently in the vicinity of the anodes. This is because of the discharge occurring in conseq emc i t b k g t g to about .01 to .20 mm. mercury column ihy' In accordance with the present invention, the previously elucidated disadvantages are done away with. Simultaneously all the advantages of the introduction of chemically inactive gas are retained. This is accomplished by providing 5 means which upon increased heating displace from the discharge gap and from the vicinity of the anodes the chemically inactive gas which entirely fills up the vessel when the latter is cold or which at least fills up the discharge gap and 10 the vicinity of the anodes. With a hot cylinder, the rare gas in the vicinity of the anodes will thereby be replaced by the stream of gas or vapor rising from the cathode, for example, by a stream of mercury vapor which, in consequence of the 15 heating of the cylinder, has attained the normal pressure for reliable operation.

The way in which the displacement of the rare gas, in conjunction with increased heating, is insured, is immaterial with regard to the fundamental inventive idea and it can be attained by any appropriate means. Suitably, for the displacement of the rare gases, a mode of flow can be utilized'which is similar to that known for mercury diffusion pumps. That is, the stream of gas or vapor, rising from the cathode, can be guided during operation in such a way, that it fills up the discharge gap and the space in the vicinity of the anodes, at the same time forcing the introduced chemically inactive gas into pre-determined parts of the vessel. This flow can be produced by cooling the upper part of the vessel more intensely than the lower part. The stream of gas or vapor, rising from the cathode, will then force back the chemically inactive gas to those parts of the vessel which are cooled best, while the anodes being situated in the vicinity of the wall parts attaining higher temperatures, will be immerged, for this reason, into an atmosphere of mercury vapor or of any other vapor or gas. For the purpose of receiving the displaced rare gas a special space or reservoir may be provided in the interior of the vessel, in which space the rare gas collects, no longer having a share in the guidance of the stream after the vessel has been heated.

In view of the fact, that the mean free lengths of path in the rare gases, for example, in argon and krypton at speeds of the electrons which correspond to the ionization voltage of these gases, are greater than the corresponding lengths of path in mercury vapor, the pressure of the rare gas, in conjunction with a cold cylinder, can be essentially lower than the pressure of the mercury vapor in conjunctionwith a hot cylinder,

in order to attain the same degree of protection against the occurrence of high-frequency oscillations, excess voltages and striking back. For instance, it has been ascertained in connection with an anode situated within an anode protective sleeve, in front of which a channel of 40 mm. length and of a diameter of 13 mm., is positioned, that .2 mm. mercury column ensures the same protection against the occurrence of disturbances in consequence of excess currents, as .04 mm. krypton. The length of the channel is the distance between the channel aperture, in which the striction cathode has been placed, and the anode surface. For the purpose of attaining with a cold cylinder the same carrying capacity as with a hot cylinder, the pressure of the rare gas need only to amount to a fraction of the pressure of the mercury vapor, amounting, as shown in the foregoing example, to but one fifth. The quantity of krypton, which fills up the entire vacuum vessel when the cylinder is cold, can then, with a hot cylinder, for example, at a temperature of from to be compressed to one fifth of its volume. Thus, the size of the reservoir for collecting the rare gas is to be dimensioned accordingly.

When using baffles situated in front of the anode protective sleeves, the pressure of the gas or vapor must be so regulated that it is above the limit at which the saturation current per channel, depending upon the gas or vapor pressure, has attained its maximum value. By saturation current per channel the following is to be understood: The maximum current value possible over a channel, as long as not all bafiles are under current, rises with increasing gas or vapor pressure, until attaining a maximum at a certain gas or vapor pressure. Above this gas or vapor pressure it will subsequently drop again. This maximum current intensity is designated as saturation current. When suitably proportioning the gas or vapor pressure and the dimensions of the baffles, the carrying capacity of the anodes may be utilized up to the limit determined by the thermic carrying capacity of the anode surface.

The pressure of the rare gas is regulated in view of the deliberations previously mentioned within the range of magnitude mentioned in my application Serial No. 745,353 according to those voltages and current intensities respectively, which the apparatus is to govern. Generally speaking, it can be said, that the gas pressure must be chosen all the higher, the greater the peaks of the current density which are admitted on the anode surface, and all the lower, the higher is the blocking voltage. The higher blocking voltage may, however, also be met with by constricting the cross section of the channel, instead of reducing the gas pressure.

With the aid of the accompanying drawings the present invention will be described in detail.

Fig. 1 represents in longitudinal section a mercury vapor rectifier in accordance with the present invention and cooled by means of air or another gaseous medium.

Fig. 2 shows in longitudinal section a mercury vapor rectifier in accordance but employing the present invention, with liquid cooling.

Fig. 3 is a longitudinal section of a mercury vapor rectifier cooled by liquid, but in which the cooling apparatus deviates from that of Fig. 2.

Fig. 4 shows in longitudinal section a rectifier with a hot cathode and cooled by means of a gaseous cooling medium.

In Fig. 1, the reference numeral I indicates the vacuum vessel proper, consisting of metal, which may, however, also consist of glass. A cathode 2 of pure mercury is situated within a container 3 of insulating material. cathode by means of the current-lead conductor 4, introduced through the inlet 5 and encased by a tube 6 of insulating material. The reference numeral 1 characterizes the anodes which are introduced in a known manner through the medium of the current-feeding conductors 8 and the inlet 9. In front of the anodes 1, which are enclosed within anode-protective sleeves I 0, baffles I I are positioned and secured to the anode-protective sleeves I0. In the interior of the vessel I is a conical screen I2 attached to the anode-protective sleeves in a suitable manner, for example, by soldering. However, special carrying means can also be provided for this screen. Between the edge of the screen and the outer walls of the 9 vessel a conduit I3 is provided. Furthermore, at the vertex of the screen an annular opening I 4 will be found. The screen I2 may, however, also be extended so as to contact with the walls of the vessel. In its upper part openings must be provided corresponding to the conduits I3. In the same way, separate holes may be drilled through the lower part of the screen in place of the annular opening I4. The annular opening I4 is guarded against the immediate stream of mercury Vapor rising from the cathode 2 by a diaphragm I5. This diaphragm I5 is carried by a tube I6, but may also be attached in any other manner. The

vessel is fitted with a cooling jacket I1, through which the fan I8 sucks a gaseous cooling medium, for example, air, from above in the downward direction, so that the upper parts of the vessel are more intensely cooled than the lower ones.

In order to promote the increased cooling of the upper part of the vessel the anodes are arranged relatively near the bottom of the vessel, so that the considerable portion of lost heat liberated at the anodes is given off preferably at the lower part of the vessel. The upper part thus remains relatively cool, and the mercury vapor pressure determined by the coolest point of the vessel can be controlled with relatively small cooling action.

The vessel is filled with a rare gas, preferably krypton, at a pressure of, for example, .04 mm. mercury column.

When starting operations, the krypton fills up the entire vessel in the first instance, so that even with a cold vessel the pressure conditions, required for operation, are present in the vessel. Now as soon as the pressure of the mercury vapor in the vicinity of the anodes has, with increasing heating attained a value of about .2 mm. mercury column, the fan I8 is started. In consequence of the more intense cooling of the upper part of the vessel and particularly, because of the strong heating of the Wall parts I9 opposite the anode tubes II), a constant stream of mercury vapor will be produced which passes along to the upper part of the walls of the vessel, where the mercury is condensed. Owing to this fiow, the krypton is gradually forced, in conjunction with increasing heating, through the conduit I3 into the space limited by the screen I2. During the operation, krypton, mixed with mercury vapor constantly emerges from the diaphragm I5 covering up the annular opening I4. This emerging gas mixture is guided by the vapor stream, rising immediately from the cathode 2, along the cool, oblique wall of the screen I2, causing the pressure of the The current is fed to the mercury vapor in this gas mixture to be reduced to the saturation value corresponding to the gas temperature. The gas mixture then flows again into the space limited by the screen. In this way larger quantities of mercury vapor cannot mix with the krypton, which would hinder the former from being condensed.

The construction illustrated in Fig. 2 diifers from that shown in Fig. 1 only in the fact, that instead of cooling by means of a gaseous medium, a liquid cooling medium is used. For the purpose of attaining a cooling of the upper part which is different from the cooling of the lower part of the vessel, the cooling space, surrounding the vessel I, has been subdivided into an upper part 26 and a lower part 2|. In conjunction with metallic vacuum vessels it will be of advantage to use a cooling liquid which contains few hydrogen ions, or none at all, or which is incapable of giving off such. Such a cooling liquid, for example, is carbon tetrachloride. The coolers have been designed as boiling coolers, the re-cooling device 22 being provided for the cooling space 20 and the recooling device 23 for the cooling space 2|. The re-coolers are connected to the cooling spaces by means of the pipings 24 and 25 and consist of blind cooling pipes. The boiling cooling liquid flows through the connecting piping into the pipes of the boiling cooler where it condenses and passes back into the cooling spaces 2!! and 2| along the bottom of the pipes 24 and 25 respectively. For the purpose of cooling the re-coolers 22 and 23, a guide channel 26 is provided, through which air or another gaseous cooling medium is sucked by means of a fan. The direction of flow of the cooling medium in connection herewith has been so chosen, that the re-cooler 22 is first reached by the fresh air, so that it will be cooled more intensely than the re-cooler 23.

In the construction according to Fig. 3, the re-coolers for the two cooling spaces 20 and 2| have not been disposed in a common channel. Instead a channel 28, as well as a fan motor 29, has been provided for the re-cooler 22, and a channel 30 and a fan motor 3| for the re-cooler 23. The fan 29 is constantly in operation, so that the upper cooling space is permanently cooled, while the fan 3| is switched 01f and on in dependence upon the temperature which the cooling space 2| assumes under the influence of the load. In this way it is assured that the upper cooling space 29 is constantly kept at a low temperature, so that a reliable separation of the rare gas from the mercury vapor may be depended upon, as long as a stream of vapor passes from the cathode in the direction of the upper cooling space 20. The fan 3|, however, works only when the lower cooling space assumes an excessive temperature, that is, when in the vicinity of the anodes the pressure of the mercury vapor attains inadmissibly high values.

For the rest, the construction shown in Fig. 3 is the same as that illustrated in Fig. 2.

In the embodiment shown in Fig. 4, an air cooling arrangement has been provided in the same way as in the construction shown in Fig. 1. Instead of a mercury cathode, however, a hot cathode 32 has been provided. Below this hot cathode a comparatively small quantity of mercury 33 is disposed. The heating of the hot cathode is eifected by means of a heating transformer 34 or by a battery in a known manner. In consequence of the waste heat of the vessel, particularly, however, through heat energy required for the hot cathode, the mercury 33 evaporates and furnishes a stream of mercury vapor rising from below in an upward direction, condenses in the upper part of the walls of the vessel, and forces the rare gas in front of it into the space or reservoir limited by the screen l2.

In all represented embodiments the rare gas thus collects in the uppermost part of the vessel as a result of the effect of streams of mercury vapor emanating from a mercury level, particularly from the cathode, so that the anodes are no longer situated in a rare gas atmosphere during operation, but in the mercury vapor atmosphere in the vicinity of the. cathodes. This embodies, further, the special advantage that, owing to the short are gap between cathode and anode, very low voltage drops will be attained.

The present invention shall not be limited either to the previously described embodiments of the cooling device, but every form will be possible which attains the purpose aimed at. Instead of providing two fans, as has been shown in Fig. 3, it will be possible in the construction according to Fig. 2 to divert the stream of cooling air so that the upper re-cooler 22 will be permanently cooled, while the lower re-cooler is only temporarily subjected to the influence of the stream of cooling air.

Under certain conditions it will be possible furthermore to guide the stream of mercury vapor by means of guide sheets, so that the rare gas is displaced in the desired manner without a different cooling of the parts of the vessel taking place. If necessary, each means may also be combined with the other.

What I claim is:

l. A vacuum discharge vessel comprising a metallic vessel, a plurality of anodes, protective sleeves for said anodes, and a mercury cathode,

said vacuum vessel having introduced thereinto a quantity of rare gas of an order of magnitude corresponding to a pressure of .01-.20 part of a millimeter of mercury. said rare gas when'the vessel is cold filling up the entire vessel and at least the discharge gap and the space in the vicinity of the anodes, and means for displacing said rare gas from the discharge gap and the space in the vicinity of the anodes upon increased heating of the vessel.

2. A gas discharge apparatus according to claim 1, in which the rare gas is one of high atomic weight.

3. A vacuum discharge vessel comprising a metallic vessel, a plurality of anodes, protective sleeves for said anodes, and a mercury cathode, said vacuum vessel having, introduced thereinto a quantity of rare gas of an order of magnitude corresponding to a pressure of .01-.20 part of a millimeter of mercury, said rare gas when the vessel is cold filling up the entire vessel and,

at least the discharge gap and the space in the vicinity of the anodes, and means for guiding the stream of vapor arising from the cathode during operation of the apparatus so that it fills up the discharge gap and the space in the vicinity of the anodes and with increased heating of the vessel displaces the rare gas into predetermined parts of the vessel.

4. In a gas discharge apparatus according to claim 1, cooling devices for cooling the upper part of the vessel more intensely than the lower part, whereby the stream of vapor rising from the cathode with increasing heat gradually disvessel, while the stream itself is partly condensed on the intensely cooled walls of the upper vessel.

5. In a gas discharge apparatus according to claim 1, said apparatus having a condensation cowl at its upper end, and cooling devices for cooling said condensation cowl more intensely than the wall parts situated adjacent the anode sleeves.

6. A vacuum discharge vessel comprising a metallic vessel, a plurality of anodes, protective sleeves for said anodes, and a mercury cathode, said vacuum vessel having introduced thereinto a quantity of rare gas of an order of magnitude corresponding to a pressure of .01-.20 parts of a millimeter of mercury, said rare gas when the vessel is cold filling up the entire vessel and at least the discharge gap and the space in the vicinity of the anodes, means for displacing the rare gas from the discharge gap and the space in the vicinity of the anodes upon increasing heating of the vessel, a cooling medium, and means for guiding said cooling medium in a downward direction in contact with the walls of said vacuum vessel.

'7. A vacuum discharge vessel comprising a metallic vessel, a plurality of anodes, protective sleeves for said anodes, and a mercury cathode, said vacuum vessel having introduced thereinto a quantity of rare gas of an order of magnitude corresponding to a pressure of .01-.20 part of a millimeter of mercury, said rare gas when the vessel is cold filling up the entire vessel and at least the discharge gap and the space in the vicinity of the anodes, means for displacing the rare gas from the discharge gap and the space in the vicinity of the anodes upon increasing heating of the vessel, a cooling medium, a cooling jacket surrounding said vacuum vessel, a gaseous cooling medium in said jacket, said cooling medium being guided so as to pass through said cooling jacket in a downward direction.

8. A vacuum discharge vessel comprising a metallic vessel, a plurality of anodes, protective sleeves for said anodes, and a mercury cathode, said vacuum vessel having introduced thereinto a quantity of rare gas of an order of magnitude corresponding to a pressure of .0l-.20 part of a millimeter of mercury, said rare gas when the vessel is cold filling up the entire vessel and at least the discharge gap and the space in the vicinity of the anodes, means for displacing said rare gas from the discharge gap and the space in the vicinity of the anodes upon increased heating of the vessel, a cooling reservoir for the upper part of the vessel, a cooling reservoir for the lower part of said vessel, a cooling medium in each, and means for cooling the cooling medium for the upper reservoir more intensely than the cooling medium for the lower reservoir.

9. In a gas discharge apparatus according to claim 1, a cooling reservoir for the upper part of the vessel, a re-cooler for said cooling reservoir, means for operating said re-cooler constantly, a cooling reservoir for the lower part of the vessel, a re-cooler for said last named reservoir, and means for operating said last named re-cooler in dependence upon the temperature of the cooling medium in said last named reser- 10. In a gas discharge apparatus according to claim 1, said vacuum vessel being divided to form a special reservoir for gradually collecting the rare gas which has been displaced during operation of the vessel with increasing heating.

11. In a gas discharge apparatus according to claim 1, cooling devices for the upper and lower parts of said vessel, means for operating said cooling devices to cool the upper part of said vessel more intensely than the lower part, a substantially conical screen disposed within the upper part of said vessel so that its vertex points downwardly, said screen being provided with inlet openings at its upper edge, and outlet openings near its lowest part for the mixture of mercury vapor and rare gas which rises during operation of the apparatus, whereby the stream of mercury vapor rising from the cathode forces the mixture escaping from the lower openings repeatedly towards the upper openings, so that the mercury vapor will condense on the intensely cooled walls of the vessel.

12. In a gas discharge apparatus according to claim 1, cooling devices for the upper and lower parts of said vessel, means for operating said cooling devices to cool the upper part of said vessel more intensely than the lower part, a substantially conical screen disposed within the upper part of said vessel so that its vertex points downwardly, said screen being provided with inlet openings at its upper edge, and outlet openings near its lowest part for the mixture of mercury vapor and rare gas which rises during operation of the apparatus, a diaphragm disposed in said screen below the lower outlet openings, said diaphragm offering protection against the stream of mixture emanating directly from the cathode.

13. In a gas discharge apparatus as defined in claim 1, said rare gas being at such pressure with respect to the pressure of the mercury vapor, that the carrying capacity of the apparatus when the vessel is cold is approximately the same as when the vessel is hot.

14. In a gas discharge apparatus according to claim 1, the pressure of the rare gas amounting to about of the pressure of the mercury vapor when the vessel is hot.

15. In a gas discharge apparatus according to claim 1, baflles disposed adjacent said anodes, the pressure within the vessel, at any given temperature of the vessel, lying above the limit at which the saturation current per channel attains its maximum value.

WALTER DALLENBACH. 

